The firing order on a Chevy V8 is 1-8-4-3-6-5-7-2.
The cylinders are numbered front to rear 1, 3, 5, and 7 on the driver's side and 2, 4, 6 and 8 on the passenger side.

If you are planning to replace your ignition wires always do one wire at a time. The #1 spark plug is the driver's side front of the engine. Trace that ignition wire to the distributor cap and you now have #1. The wires run clockwise on the distributor cap. So the next wire in line would be #8 , the next will be #4 and so on. If you already removed the wires and seem lost you can either look in a Chilton's manual and/or see the firing order in the picture diagram.

Often the intake manifold runners will be numbered to show the firing order. If all else fails try this:

Remove the #1 spark plug.

Remove the distributor cap.

Put your finger on the spark plug hole that you just removed and turn the engine over slowly. Do this until the compression stroke comes up, you will feel air pressure at this point on your finger.

Look at the timing indicator located on your timing chain cover. You should see a line scribed in the lower crankshaft pulley.

Align the TDC line on the pulley or damper outer ring with the timing tab indicating "0" or TDC. You now have top dead center.

Look at the rotor. It will point to #1 on your distributor cap. The wire that plugs into this terminal in the cap can be called #1. Connect the other end to the spark plug on the driver's side front. Continue by following the direction of rotation to attach the remainder of the plug wires following the firing order.